The French published patent application No. FR 2 508 579A describes a knuckle joint for articulating a first bar to a second bar, the knuckle joint comprising generally a spherical knuckle piece carried by the first bar and a rotary socket carried by the second bar. The socket cooperates with the knuckle member so that the bars are able to move with respect to each other in a "universal" movement, whereby relative rotation can take place between the two bars and also relative tilting movement in planes containing the axis of the rotational movement.
In order to limit the inclination, or angle through which the tilting movement takes place, there may be provided, as disclosed in French patent specification No. 1 504 620, an end stop element for the tilting movement whereby the edge of the open surface of the rotary socket cooperates with a cylindrical sleeve which is provided between the knuckle piece and the bar which carries the latter.
An arrangement having the above features has the disadvantages, firstly that an additional member, namely the sleeve between the knuckle piece and the bar which carries it, has to be provided; and secondly the opening which is formed in the open side of the rotary socket is restricted by virtue of the stop element. This necessitates, in order that the knuckle piece can be mounted by a snap fit within the socket, either the exertion of a high force which introduces the risk of damage to the knuckle joint itself, or the provision of additional apertures to relieve the open side of the socket so as to allow the resilience of the edge of the opening to be increased; and this can only complicate the structure of the rotary socket.